I've recently bought a 3DS XL with one DS game. It's my first true Nintendo handheld console, and it's pretty nice to have one. I've used emulators in the past on phones, PSP, etc. so have not missed everything Nintendo had to offer.

Anyway, I've been reading some threads, seems like 'flashcarts' is the tool needed to play some ROMs on the 3DS. I see Supercard DSTwo is a favourite but I will only use the DS-gaming aspect (I understand 3DS gaming is still not possible) and will not use GBA, SNES, etc. emulation as I've played most of 'em already and have the whole DS library to sink my teeth into (didn't DS emulate on PCs much). DSTwo still good idea?

At the moment, my 3DS XL is on ver. 4.5.0-10E. Not entirely sure how the flashcarts work, but am I 'too up to date' for most carts out there? How do flash carts update their FWs? Just manual downloads from their sites?

I'm in UK if this is needed.

To summarise:
Which flashcart would work for my needs -
3DS XL
DS-gaming only

Also, would a standard 2GB MicroSD work on these carts (I understand the size is not ideal for ROMs)?

I recommend Supercard DSTwo if you can afford it. I also have an R4, I haven't even had it that long and it's blocked on 3DS (its a Rev C but the wrong one). You can get the R4 cheaper but make sure to get the one that's not blocked. Yes most cards are blocked on your 3DS firmware so these are pretty much the 2 to choose from.

Future updates are more likely to block your R4 but I don't think they will ever be able to block the DSTwo. Also R4 has lots of hardware revisions while DSTwo has just one version. Lots of us have been waiting for awhile for our R4 versions to become unblocked.

The DSTWO only survived because it has its own processor and was able to disable a common flashcard part with an update and keep running. The latest Nintendo patch pretty much blocked all the popular and cheap ones.

I use R4i Gold 3DS for my recently bought 3DS XL with 16gb micro card. the NDS roms works fine. But I did not test if I can play online through wifi and I don't know if it's wise to do maybe Nintendo can see.

2GB works, but you might not be able to hold as many games as you want, as they can be up to 512MB in size (though more are 32-128MB). Flash carts support up to 32GB officially, most people go 4GB or 8GB depending on how many games they want to stock up with at once.